A ROM FUSE block to store defect information of memory cells in a block unit or a column unit may be provided in a memory cell array.
The ROM FUSE block has a size equal to a size of a normal block and includes a plurality of memory cells. When a defect beyond an allowable limit occurs in the memory cells of the ROM FUSE block, ROM FUSE data itself stored in the ROM FUSE block may become defective. In addition, when a defect occurs in the ROM FUSE data, it takes time to correct an error, which may result in decreasing an operation speed of a semiconductor storage device. Particularly, when the memory cells are miniaturized, the memory cells are likely to become defective. For this reason, a defect check of the ROM FUSE block becomes important.
The defect check of the ROM FUSE block is generally executed during a power-on read period after power is supplied.
However, when the memory cells are miniaturized, an erasure level is likely to change, a difference of the erasure level and a read level decreases, and erroneous read is more likely to occur.
If the memory cell is miniaturized and a memory capacity increases, the number of blocks also increases and defect information to be recorded in the ROM FUSE block also increases. For this reason, it takes time to read the defect information from the ROM FUSE block.